Composite membranes having intrinsic microporosity

ABSTRACT

The present invention relates to a composite membrane for gas separation and/or nanofiltration of a feed stream solution comprising a solvent and dissolved solutes and showing preferential rejection of the solutes. The composite membrane comprises a separating layer with intrinsic microporosity. The separating layer is suitably formed by interfacial polymerization on a support membrane. Suitably, at least one of the monomers used in the interfacial polymerization reaction should possess concavity, resulting in a network polymer with interconnected nanopores and a membrane with enhanced permeability. The support membrane may be optionally impregnated with a conditioning agent and may be optionally stable in organic solvents, particularly in polar aprotic solvents. The top layer of the composite membrane is optionally capped with functional groups to change the surface chemistry. The composite membrane may be cured in the oven to enhance rejection. Finally, the composite membrane may be treated with an activating solvent prior to nanofiltration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry under 35 USC § 371(b) of PCTInternational Application No. PCT/GB2012/052576, filed Oct. 18, 2012,which claims priority to United Kingdom Patent Application No.1117950.4, filed Oct. 18, 2011, the entire disclosures of both of whichare incorporated herein by reference.

The work leading to this invention has received funding from theEuropean Union Seventh Framework Programme (FP7/2007-2013) under grantagreement no 241226.

FIELD OF INVENTION

The present invention relates to separation membranes. Morespecifically, the present invention relates to thin film compositemembranes comprising a support membrane coated with a separating layer,wherein the separating layer comprises a network polymer possessingintrinsic microporosity. The present invention also relates to processesfor the preparation of these membranes and their use in a variety ofapplications, including, but not limited to, gas separation,pervaporation, nanofiltration, desalination and water treatment, andparticularly the nanofiltration of solutes dissolved in organicsolvents.

BACKGROUND TO THE INVENTION

Membrane processes have been widely applied in separation science, andcan be applied to a range of separations of species of varying molecularweights in liquid and gas phases (see for example “Membrane Technologyand Applications” 2^(nd) Edition, R. W. Baker, John Wiley and Sons Ltd,ISBN 0-470-85445-6).

With particular reference to nanofiltration, such applications havegained attention based on the relatively low operating pressures, highfluxes and low operation and maintenance costs associated therewith.Nanofiltration is a membrane process utilising membranes with molecularweight cut-off in the range of 200-2,000 Daltons. Molecular weightcut-off of a membrane is generally defined as the molecular weight of amolecule that would exhibit a rejection of 90% when subjected tonanofiltration by the membrane.

Membranes for nanofiltration, pervaporation and gas separation aregenerally fabricated by making composite membranes. Thin film compositemembranes may be fabricated via interfacial polymerization (herein alsoreferred to as IP) or by coating [Lu, X.; Bian, X.; Shi, L.,“Preparation and characterization of NF composite membrane.” J. Membr.Sci., 210, 3-11, 2002].

In glassy polymers, gas permeability depends strongly on the amount anddistribution of free volume in the polymer (i.e. the space not occupiedby polymer molecules) and on chain mobility. In liquid applications whenusing defect-free thin film composite membranes, high free volume leadsto high permeability. Polymers with the highest permeabilities haverigid, twisted macromolecular backbones that give rise to microvoids.When the free volume is very high, these microvoids are interconnectedresulting in intrinsic microporosity. Here, microporous materials aresolids having interconnected pores of less than 2 nm in size [Handbookof Porous Solids, Schuth F, Sing K, Weitkamp J. Eds. Wiley-VCH; Berlin2002, Vols 1-5]. This size of porosity is also commonly referred to asnanoporosity, and materials with this microporosity are referred to asbeing nanoporous.

To achieve very high permeabilities, high free volume and microporosityare sought after. Polymers presenting these properties are so-calledhigh free volume polymers. These highly permeable polymers have beenapplied mostly to gas separations. Some examples include certainsubstituted polyacetylenes (e.g. PTMSP), some perfluoropolymers (e.g.Teflon AF), certain poly(norbornene)s, polymers of intrinsicmicroporosity, and some polyimides. Their microporosity has beendemonstrated by molecular modelling and positron lifetime spectroscopy(PALS). Highly permeable polyacetylenes have bulky side groups thatinhibit conformational change and force the backbone into a twistedshape. These rigid polymer macromolecules cannot pack properly in thesolid state, resulting in high free volume. The free volume distributioncomprises disconnected elements as in glassy polymers and continuousmicrovoids. In Teflon perfluoropolymers their high free volume is due toa high barrier to rotation between neighbouring dioxolane rings, coupledwith weak interchain interactions, which are well known forfluoropolymers, leading to low packing density and hence highpermeability. In the case of poly(norborene)s and PTMSP, the presence ofbulky trimethylsilyl groups on the ring greatly restricts the freedom ofthe polymer to undergo conformational change. In polymers of intrinsicmicroporosity (PIMs), molecular linkers containing points of contortionare held in non-coplanar orientation by rigid molecules, which do notallow the resulting polymers to pack closely and ensure highmicroporosity. The PIMs concept has been reported for polymides [P MBudd and N B McKewon, “Highly permeable polymers for gas separationmembranes, Polymer Chemistry, 1, 63-68, 2010].

There are two different types of PIMs, i) non-network (linear) polymerswhich may be soluble in organic solvents, and ii) network polymers whichare generally insoluble, depending on the monomer choice. PIMs possessinternal molecular free volume (IMFV), which is a measure of concavityand is defined by Swager as the difference in volume of the concave unitas compared to the non-concave shape [T M Long and T M Swager,“Minimization of Free Volume: Alignment of Triptycenes in LiquidCrystals and Stretched Polymers”, Adv. Mater, 13, 8, 601-604, 2001].While the intrinsic microporosity in linear PIMs is claimed to derivefrom the impenetrable concavities given by their contorted structures,in network PIMs, microporosity is also claimed to derive from theconcavities associated with macrocycles. In non-network PIMs, rotationof single bonds has to be avoided, whereas the branching andcrosslinking in network PIMs is thought to avoid structuralrearrangement that may result in the loss of microporosity (McKeown,2010), so that single bonds can be present without loss ofmicroporosity. In general, it has been observed that network PIMspossess greater microporosity than non-network PIMs due to theirmacrocyclization [N B McKewon, P M Budd, “Explotation of IntrinsicMicroporosity in Polymer-Based materials”, Macromolecules, 43,5163-5176, 2010]. However, since prior art network PIMs are not soluble,they can only be incorporated into a membrane if mixed as fillers withmicroporous soluble materials, which include soluble PIMs or othersoluble polymers. There is a strict requirement in non-network PIMs thatthere are no single bonds in the polymer backbone, to prevent rotationalfreedom and so provide intrinsic microporosity. Highly rigid andcontorted molecular structures are required, providing awkwardmacromolecular shapes that cannot pack efficiently in space. Moleculeswith awkward shapes are those that pose packing problems due to theirconcavities. However, in order to have microporosity in non-networkPIMs, concave shape molecules are not sufficient as the voids must besufficiently interconnected for transport to occur with minimal energy(i.e. intrinsic microporosity) [N B McKewon, P M Budd, “Explotation ofIntrinsic Microporosity in Polymer-Based materials”, Macromolecules, 43,5163-5176, 2010]. Non-network PIMs may be soluble, and so suitable forcasting a membrane by phase inversion, or for use coating a supportmembrane to make a thin film composite. However, their solubility in arange of solvents restricts their applications in organic solventnanofiltration [Ulbricht M, Advanced functional polymer membranes.Single Chain Polymers, 47, 2217-2262, 2006].

U.S. Pat. No. 7,690,514 B2 describes materials of intrinsicmicroporosity comprising organic macromolecules comprised of a firstgenerally planar species connected by linkers having a point ofcontortion such that two adjacent first planar species connected by alinker are held in non-coplanar orientation. Preferred points ofcontortion are spiro groups, bridged ring moieties and stericallycongested bonds around which there is restricted rotation. Thesenon-network PIMs may be soluble in common organic solvents, allowingthem to be cast into membranes, or coated onto other support membranesto make a thin film composite.

PIM-1 (soluble PIM) membranes exhibit gas permeabilities which areexceeded only by very high free volume polymers such as Teflon AF2400and PTMSP, presenting selectivities above Robenson's 1991 upper boundfor gas pairs such as CO₂/CH₄ and O₂/N₂. Studies have shown thatpermeability is enhanced by methanol treatment, helping flush outresidual casting solvent and allowing relaxation of the chains [P M Buddand N B McKewon, D Fritsch, “Polymers of Intrinsic Microporosity (PIMs):High free volume polymers for membrane applications”, Macromol Symp,245-246, 403-405, 2006].

A range of polyimides with characteristics similar to a polymer ofintrinsic microporosity (PIM) were prepared by Ghanem et al. andmembrane gas permeation experiments showed these PIM-Polyimides to beamong the most permeable of all polyimides and to have selectivitiesclose to the upper bound for several important gas pairs [B G Ghanem, NB McKeown, P M Budd, N M Al-Harbi, D Fritsch, K Heinrich, LStarannikova, A Tokarev and Y Yampolskii, “Synthesis, characterization,and gas permeation properties of a novel group of polymers withintrinsic micro porosity: PIM-polyimides”, Macromolecules, 42,7781-7888, 2009].

U.S. Pat. No. 7,410,525 B1, describes polymer/polymer mixed matrixmembranes incorporating soluble polymers of intrinsic microporosity asmicroporous fillers for use in gas separation applications.

International Patent Publication No. WO 2005/113121 (PCT/GB2005/002028)describes the formation of thin film composite membranes from PIMs bycoating a solution of PIMs in organic solvent onto a support membrane,and then optionally crosslinking this PIM film to enhance its stabilityin organic solvents.

In order to improve the stability of soluble-PIMs membranes U.S. Pat.No. 7,758,751 B1, describes high performance UV-crosslinked membranesfrom polymers of intrinsic microporosity (PIMs) and their use in bothgas separations, and liquid separations involving organic solvents suchas olefin/paraffin, deep desulfurization of gasoline and diesel fuels,and ethanol/water separations.

Organic Solvent Nanofiltration (OSN) has many potential applications inmanufacturing industries including solvent exchange, catalyst recoveryand recycling, purifications, and concentrations. U.S. Pat. Nos.5,174,899; 5,215,667; 5,288,818; 5,298,669 and 5,395,979 disclose theseparation of organometallic compounds and/or metal carbonyls from theirsolutions in organic media. UK Patent No. GB 2,373,743 describes theapplication of OSN to solvent exchange; UK Patent No. GB 2,369,311describes the application of OSN to recycle of phase transfer agents,and; European Patent Application EP1590361 describes the application ofOSN to the separation of synthons during oligonucleotide synthesis.

Membranes for reverse osmosis and nanofiltration can be made by theinterfacial polymerisation (IP) technique. In the IP technique, anaqueous solution of a first reactive monomer (often a polyamine) isfirst deposited within the porous structure of a support membrane, oftena polysulfone ultrafiltration membrane. Then, the polysulfone supportmembrane loaded with the reactive monomer solution is immersed in awater-immiscible solvent solution containing a second reactive monomer,such as triacid chloride in hexane. The first and second reactivemonomers react at the interface of the two immiscible solutions, until athin film presents a diffusion barrier and the reaction is completed toform a highly cross-linked thin film layer that remains attached to thesupport membrane. The thin film layer can be from several tens ofnanometers to several micrometers thick. The IP technique is well knownto those skilled in the art [Petersen, R. J. “Composite reverse osmosisand nanofiltration membranes”. J. Membr. Sci, 83, 81-150, 1993]. Thethin film is selective between molecules, and this selective layer canbe optimized for solute rejection and solvent flux by controlling thereaction conditions, characteristics of the reactive monomers, solventschosen and post-reaction treatments. The porous support membrane can beselectively chosen for porosity, strength and solvent stability. Aparticularly preferred class of thin film materials for nanofiltrationare polyamides formed by interfacial polymerization. Examples of suchpolyamide thin films are found in U.S. Pat. Nos. 5,582,725, 4,876,009,4,853,122, 4,259,183, 4,529,646, 4,277,344 and 4,039,440, the pertinentdisclosures of which are incorporated herein by reference.

U.S. Pat. No. 4,277,344 describes an aromatic polyamide membraneproduced by the interfacial polymerization of an aromatic polyamine withat least two primary amine substituents and an acyl halide having atleast three acyl halide substituents. Wherein, the aqueous solutioncontains a monomeric aromatic polyamine reactant and the organicsolution contains an amine-reactive polyfunctional acyl halide. Thepolyamide layer of TFC membranes is typically obtained via aninterfacial polymerization between a piperazine or an amine substitutedpiperidine or cyclohexane, and a polyfunctional acyl halide as describedin U.S. Pat. Nos. 4,769,148 and 4,859,384. A way of modifying reverseosmosis (herein also referred to as RO) TFC membranes for nanofiltrationis described in U.S. Pat. Nos. 4,765,897; 4,812,270; and 4,824,574.Post-interfacial polymerization treatments have also been used toincrease the pore size of TFC RO membranes. U.S. Pat. No. 5,246,587describes an aromatic polyamide RO membrane that is made by firstcoating a porous support material with an aqueous solution containing apolyamine reactant and an amine salt. Examples of suitable polyaminereactants provided include aromatic primary diamines (such as,m-phenylenediamine or p-phenylenediamine or substituted derivativesthereof, wherein the substituent is an alkyl group, an alkoxy group, ahydroxy alkyl group, a hydroxy group or a halogen atom; aromaticsecondary diamines (such as, N,N-diphenylethylene diamine),cycloaliphatic primary diamines (such as cyclohexane diamine),cycloaliphatic secondary diamines (such as, piperazine or trimethylenedipiperidine); and xylene diamines (such as m-xylene diamine).

In another method described in U.S. Pat. No. 6,245,234, a TFC polyamidemembrane is made by first coating a porous polysulfone support with anaqueous solution containing: 1) a polyfunctional primary or secondaryamine; 2) a polyfunctional tertiary amine; and; 3) a polar solvent. Theexcess aqueous solution is removed and the coated support is then dippedin an organic solvent solution of trimesoyl chloride (TMC) and a mixtureof alkanes having from eight to twelve carbon atoms.

Many different types of polymers may be interfacially synthesized usinginterfacial polymerization. Polymers typically used in interfacialpolymerization applications include, but are not limited to, polyamides,polyurea, polypyrrolidines, polyesters, poly(ester amides),polyurethanes, polysiloxanes, poly(amide imides), polyimides, poly(etheramides), polyethers, poly(urea amides) (PUA) [Petersen, R. J. “Compositereverse osmosis and nanofiltration membranes”. J. Membr. Sci, 83,81-150, 1993]. For example, U.S. Pat. No. 5,290,452 describes theformation of a crosslinked polyesteramide TFC membrane produced viainterfacial polymerization. The membrane is made by reacting adianhydride (or its corresponding diacid-diester) with a polyester diolto produce an end-capped prepolymer. The resulting end-capped prepolymeris then reacted with excess thionyl chloride to convert all unreactedanhydride and all carboxylic-acid groups into acid chloride groups. Theresulting acid-chloride derivative is dissolved in organic solvent andinterfacially reacted with a diamine dissolved in an aqueous phase.

In order to improve the stability of TFC prepared by interfacialpolymerisation, poly(esteramide) based TFC membranes have been developedshowing improved oxidative (chlorine) resistance compared to polyamidemembranes [M. M. Jayaraniand S. S. Kulkarni, “Thin-film compositepoly(esteramide)-based membranes”, Desalination, 130, 17-30, 2000]. Ithas been reported that the rejection of polyesteramide TFC membranes canbe tailored by varying the ester/amide ratio; more open TFC membraneswere prepared using bisphenols with bulky substituents for diafiltrationto separate organic molecules (MW>400 Da) from salts [Uday Razadan andS. S. Kulkarni, “Nanofiltration thin-film composite polyesteramidemembranes based on bulky diols”, Desalination, 161, 25-32, 2004].

U.S. Pat. No. 5,593,588 describes a thin film composite reverse osmosismembrane having an active layer of aromatic polyester or copolymer ofaromatic polyester and aromatic polyamide, which has improvedchlorine-resistance and oxidation stability. The active layer isprepared by the interfacial polymerization of an aqueous solution ofpolyhydric phenol and a solution of aromatic acyl halide dissolved inorganic solvent. Spiral-wound poly(ether/amide) thin film compositemembranes designated PA-300, have been previously reported for waterdesalination applications. PA-300 was formed by an in situ interfacialpolymerization of an aqueous solution of epichlorohydrin-ethylenediamine and an organic solution of isophthalyldichloride [R L Riley, R LFox, C R Lyons, C E Milstead, M W Seroy, and M Tagami, “Spiral-woundpoly(ether/amide) Thin-Film composite membrane systems”, Desalination,19, 113-126, 1976].

The support membranes generally used for commercial TFC membranes madeby interfacial polymerisation are often polysulfone or polyethersulfoneultrafiltration membranes. These supports have limited stability fororganic solvents and, therefore, thin film composite membranes of theprior art which are fabricated with such supports cannot be effectivelyutilized for all organic solvent nanofiltration applications.

Although interfacially polymerized TFC membranes of the prior art havebeen specifically designed to separate aqueous feed streams down to amolecular level, they can be applied in certain organic solvents as well[Koseoglu, S. S., Lawhon, J. T. & Lusas, E. W. “Membrane processing ofcrude vegetable oils pilot plant scale removal of solvent from oilmiscellas”, J. Am. Oil Chem. Soc. 67, 315-322, 1990, U.S. Pat. No.5,274,047]. Their effectiveness depends on the specific molecularstructure of the thin film layer and the stability of the supportmembrane. U.S. Pat. No. 5,173,191, suggests nylon, cellulose, polyester,Teflon and polypropylene as organic solvent resistant supports. U.S.Pat. No. 6,986,844 proposes the use of crosslinked polybenzimidazole formaking suitable support membranes for TFC. TFC membranes comprising athin film synthesized from piperazine/m-phenylenediamine and trimesoylchloride on a PAN support membrane performed well in methanol, ethanoland acetone, less well in i-propanol and MEK, and gave no flux in hexane[Kim, I.-C., Jegal, J. & Lee, K.-H. “Effect of aqueous and organicsolutions on the performance of polyamide thin-film-compositenanofiltration membranes.” Journal of Polymer Science Part B: PolymerPhysics 40, 2151-2163, 2002].

US 2008/0197070 describes the formation of thin film composite membraneson polyolefin (e.g. polypropylene) supports prepared by interfacialpolymerization. These membranes performed well in water, ethanol andmethanol.

Non-reactive polydimethylsiloxane (PDMS) has been added during theinterfacial polymerization reaction using polyacrylonitrile (PAN) as thesupport membrane [Kim, I. C. & Lee, K. H. “Preparation of interfaciallysynthesized and silicone-coated composite polyamide nanofiltrationmembranes with high performance.” Ind. Eng. Chem. Res. 41, 5523-5528,2002, U.S. Pat. No. 6,887,380, U.S. Pat. Applic No. 0098274 2003]. Theresulting silicone-blended PA membrane showed high hexanepermeabilities.

TFC membranes have also been applied for filtration in apolar solvents.A method for the separation of lube oil from organic solvents (e.g.furfural, MEK/toluene, etc.) with a TFC membrane using poly(ethyleneimine) and a diisocyanate on a solvent resistant nylon 6,6 support hasbeen described in U.S. Pat. No. 5,173,911.

In interfacially polymerized composite membranes, both the surfacechemistry and the morphology of the support membrane play a crucial rolein determining the overall composite membrane performance. Membraneperformance can be enhanced through modification of the membrane surface[D. S. Wavhal, E. R. Fisher, “Membrane surface modification byplasma-induced polymerization of acrylamide for improved surfaceproperties and reduced protein fouling”, Langmuir 19, 79, 2003]. Thus,different procedures have been carried out to chemically modify themembrane surface and modify its properties. These procedures mayincrease the hydrophilicity, improve selectivity and flux, adjusttransport properties, and enhance resistance to fouling and chlorine.Many methods have been reported for membrane surface modification suchas grafting, coating [U.S. Pat. No. 5,234,598, 5,358,745, 6,837,381] andblending of hydrophilic/-phobic surface modifying macromolecules (SMMs)[B. J. Abu Tarboush, D. Rana, T. Matsuura, H. A. Arafat, R. M. Narbaitz,“Preparation of thin-film-composite polyamide membranes for desalinationusing novel hydrophilic surface modifying macromolecules”, J. Membr.Sci. 325, 166, 2008].

In order to improve the performance of TFC membranes, differentconstituents have been added to the amine and/or acyl halide solutions.For example, U.S. Pat. No. 4,950,404, describes a method for increasingflux of a TFC membrane by adding a polar aprotic solvent and an optionalacid acceptor to the aqueous amine solution prior to the interfacialpolymerization reaction. In a similar way, U.S. Pat. Nos. 5,989,426;6,024,873; 5,843,351; 5,614,099; 5,733,602 and 5,576,057 describe theaddition of selected alcohols, ketones, ethers, esters, halogenatedhydrocarbons, nitrogen-containing compounds and sulfur-containingcompounds to the aqueous amine solution and/or organic acid halidesolution prior to the interfacial polymerization reaction.

It has been claimed that soaking freshly prepared TFC membranes insolutions containing various organic species, including glycerol, sodiumlauryl sulfate, and the salt of triethylamine with camphorsulfonic acidcan increase the water flux in RO applications by 30-70% [M. A. Kuehne,R. Q. Song, N. N. Li, R. J. Petersen, “Flux enhancement in TFC ROmembranes”, Environ. Prog. 20 (1), 23, 2001]. As described in U.S. Pat.Nos. 5,234,598 and 5,358,745, TFC membrane physical properties (abrasionresistance), and flux stability can also be improved by applying anaqueous solution composed of poly(vinyl alcohol) (PVA) and a buffersolution as a post formation step during membrane preparation. Addingalcohols, ethers, sulfur-containing compounds, monohydric aromaticcompounds and more specifically dimethyl sulfoxide (DMSO) in the aqueousphase can produce TFC membranes with an excellent performance [S.-Y.Kwak, S. G. Jung, S. H. Kim, “Structure-motion-performance relationshipof flux-enhanced reverse osmosis (RO) membranes composed of aromaticpolyamide thin films”, Environ. Sci. Technol. 35, 4334, 2001; U.S. Pat.No. 5,576,057; 5,614,099]. After addition of DMSO to the interfacialpolymerization system, TFC membranes with water flux five times greaterthan the normal TFC water flux with a small loss in rejection wereobtained [S. H. Kim, S.-Y. Kwak, T. Suzuki, “Positron annihilationspectroscopic evidence to demonstrate the flux-enhancement mechanism inmorphology-controlled thin-film-composite (TFC) membrane”, Environ. Sci.Technol. 39, 1764, 2005].

However, in these prior art TFC membranes the use of a polysulfonesupport membrane limits the potential for additives to either aqueousamine solution or organic acid halide solution.

Several methods for improving TFC membrane performance post-formationare also known. For example, U.S. Pat. No. 5,876,602 describes treatingthe TFC membrane with an aqueous chlorinating agent to improve flux,lower salt passage, and/or increase membrane stability to bases. U.S.Pat. No. 5,755,965 discloses a process wherein the surface of the TFCmembrane is treated with ammonia or selected amines, e.g., 1,6, hexanediamine, cyclohexylamine and butylamine. U.S. Pat. No. 4,765,879describes the post treatment of a membrane with a strong mineral acidfollowed by treatment with a rejection enhancing agent.

A method of chemical treatment is claimed to be able to cause asimultaneous improvement of water flux and salt rejection of thin-filmcomposite (TFC) membranes for reverse osmosis [Debabrata Mukherjee,Ashish Kulkarni, William N. Gill, “Chemical treatment for improvedperformance of reverse osmosis membranes”, Desalination 104, 239-249,1996]. Hydrophilization by treating the membrane surface with watersoluble solvent (acids, alcohols, and mixtures of acids, alcohols andwater) is a known surface modification technique. This method increasesthe flux without changing the chemical structure [Kulkarni, D.Mukherjee, W. N. Gill, “Flux enhancement by hydrophilization of thinfilm composite reverse osmosis membranes”, J. Membr. Sci. 114, 39,1996]. Using a mixture of acid and alcohol in water for the surfacetreatment can improve the surface properties, since acid and alcohol inwater cause partial hydrolysis and skin modification, which produces amembrane with a higher flux and a higher rejection. It was suggestedthat the presence of hydrogen bonding on the membrane surface encouragesthe acid and water to react on these sites producing more charges [D.Mukherjee, A. Kulkarni, W. N. Gill, “Flux enhancement of reverse osmosismembranes by chemical surface modification”, J. Membr. Sci. 97, 231,1994]. Kulkarni et al. hydrophilized a TFC—RO membrane by using ethanol,2-propanol, hydrofluoric acid and hydrochloric acid. They found thatthere was an increase in hydrophilicity, which led to a remarkableincrease in water flux with no loss in rejection.

A hydrophilic, charged TFC can be achieved by using radical grafting oftwo monomers, methacrylic acid and poly(ethylene glycol) methacrylateonto a commercial PA-TFC—RO membrane [S. Belfer, Y. Purinson, R.Fainshtein, Y. Radchenko, O. Kedem, “Surface modification of commercialcomposite polyamide reverse osmosis membranes”, J. Membr. Sci. 139, 175,1998]. It was found that the use of amine containing ethylene glycolblocks enhanced the performance of the membrane, and highly improvedmembrane water permeability by increasing hydrophilicity [M. Sforga, S.P. Nunes, K.-V. Peinemann, “Composite nanofiltration membranes preparedby in-situ polycondensation of amines in a poly(ethylene oxide-b-amide)layer”, J. Membr. Sci. 135, 179, 1997]. Poly(ethylene glycol) (PEG) andits derivatives have been used for surface modification. TFC membraneresistance to fouling could be improved by grafting PEG chains onto theTFC—RO membranes [G. Kang, M. Liu, B. Lin, Y. Cao, Q. Yuan, “A novelmethod of surface modification on thin-film composite reverse osmosismembrane by grafting poly(ethylene glycol)”, Polymer 48, 1165, 2007, V.Freger, J. Gilron, S. Belfer, “TFC polyamide membranes modified bygrafting of hydrophilic polymers: an FT-IR/AFM/TEM study”, J. Membr.Sci. 209, 283, 2002].

PEG has also been used to improve the TFC membrane formation[Shih-Hsiung Chen, Dong-Jang Chang, Rey-May Liou, Ching-Shan Hsu,Shiow-Shyung Lin, “Preparation and Separation Properties of PolyamideNanofiltration Membrane”, J Appl Polym Sci, 83, 1112-1118, 2002].Because of the poor hydrophilicity of the polysulfone support membrane,poly(ethylene glycol) (PEG) was added to the aqueous solution as awetting agent. The effect of PEG concentration on the resulting membraneperformance was also studied.

It has been reported that PEG is frequently used as an additive in thepolymer solution to influence the membrane structure during phaseinversion [Y. Liu, G. H. Koops, H. Strathmann, “Characterization ofmorphology controlled polyethersulfone hollow fiber membranes by theaddition of polyethylene glycol to the dope and bore liquid solution”,J. Membr. Sci. 223, 187, 2003] The role of these additives is to createa spongy membrane structure by prevention of macrovoid formation andenhance pore formation during phase inversion. Other frequently usedadditives are: glycerol, alcohols, dialcohols, water, polyethylene oxide(PEO), LiCl and ZnCl₂. US patent Nos. 2008/0312349 A and 2008/207822 Aalso describe the use of PEG in the polymeric dope solution duringpreparation of microporous support membranes.

It is generally known that heating, also known as curing, of thin filmcomposite membranes can be required to facilitate the removal of organicsolvent from nascent polyamide thin films, and to promote additionalcrosslinking by dehydration of unreacted amine and carboxyl groups.[Asim K. Ghosh, Byeong-Heon Jeong, Xiaofei Huang, Eric M. V. Hoek,Impacts of reaction and curing conditions on polyamide composite reverseosmosis membrane properties, Journal of Membrane Science 311 (2008)34-45]. This heating or curing is usually undertaken after theinterfacial polymerisation reaction, and can be in the range from 45° C.to 90° C. or higher.

The membrane products and membrane-related methods of the presentinvention advantageously address and/or overcome the obstacles,limitations and problems associated with current membrane technologiesand effectively address membrane-related needs that are noted herein.

SUMMARY OF THE INVENTION

The present invention provides, in a first aspect, a thin film compositemembrane comprising a support membrane coated with a separating layer,wherein the separating layer comprises a network polymer possessingintrinsic microporosity. The membranes of the invention are particularlysuitable for gas separation, pervaporation, nanofiltration, desalinationand water treatment.

Suitably, at least a proportion of the monomeric components of thenetwork polymer possess concavity.

More particularly, the present invention relates to the production andutilization of membranes for nanofiltration operations in organicsolvents.

Further, the present invention also provides thin film compositemembranes formed by interfacial polymerisation. Thus, in another aspect,the present invention provides a thin film composite membrane comprisinga support membrane coated with a separating layer, wherein theseparating later is formed on the support layer by interfacialpolymerisation, and wherein the separating layer comprises a networkpolymer possessing intrinsic microporosity.

In a particular embodiment, the thin film composite membranes are formedby interfacial polymerisation, wherein at least one of the monomers usedin the interfacial polymerisation reaction possesses concavity.

In another aspect, the invention provides a thin film compositemembrane, wherein the membrane is a composite membrane comprising aseparating layer formed by interfacial polymerisation of at least onefirst reactive monomer and at least one second reactive monomer on asupport membrane, wherein the resulting separating layer comprises apolymer network with intrinsic microporosity. The support membrane maybe impregnated with a conditioning agent and may be stable in organicsolvents; and wherein the composite membrane may be cured withtemperature and/or treated with an activating solvent prior to use.Suitably, at least one of the reactive monomers used in the interfacialpolymerisation reaction is a molecule with a concave shape (i.e. awkwardor contorted) preferably rigid, restricting the freedom of the resultingnetwork polymer to undergo structural rearrangement, giving rise tointerconnected microvoids and associated intrinsic microporosity.

In an embodiment, the composite membrane may be cured with temperaturefor a given time to improve some properties, including, but not limitedto, membrane selectivity.

In a further embodiment, the composite membrane may be treated with anactivating solvent during or after interfacial polymerisation. Withoutwishing to be bound by any particular theory, the use of an activatingsolvent to treat the membrane is believed to flush out any debris,unreacted material and small oligomers from the pores of the membranefollowing the interfacial polymerisation reaction. The treatment of thecomposite membrane with an activating solvent provides a membrane withimproved properties, including, but not limited to, membrane flux.

In a further aspect, the invention provides an interfacialpolymerisation process for forming a thin film composite membrane asdefined herein, comprising the steps of:

-   (a) impregnating a porous support membrane which may comprise a    first conditioning agent, with a first reactive monomer solution    comprising:    -   (i) a first solvent for the said first reactive monomer;    -   (ii) a first reactive monomer or/and a reactive monomer        possessing concavity;    -   (iii) optionally, an activating solvent,    -   (iv) optionally, additives including alcohols, ketones, ethers,        esters, halogenated hydrocarbons, nitrogen-containing compounds        and sulphur-containing compounds, monohydric aromatic compounds;-   (b) contacting the impregnated support membrane with a second    reactive monomer solution comprising:    -   (i) a second solvent for the second reactive monomer;    -   (ii) a second reactive monomer or/and a reactive monomer        possessing concavity;    -   (iii) optionally, additives including alcohols, ketones, ethers,        esters, halogenated hydrocarbons, nitrogen-containing compounds        and sulphur-containing compounds, monohydric aromatic compounds;        wherein:    -   the first solvent and the second solvent form a two phase        system;    -   at least one of the reactive monomers possesses concavity; and    -   the reaction of the monomers results in a separating layer        forming on the support membrane to give a composite membrane;-   (c) optionally, after a reaction period, capping the unreacted    groups of the separating layer with functional groups to modify the    surface chemistry;-   (d) after a reaction period, immersing the resulting composite    membrane into a quench medium;-   (e) optionally, curing the membrane with temperature or microwaves    for a given time;-   (f) optionally, treating the resulting composite membrane with an    activating solvent; and-   (g) optionally, impregnating the resulting composite membrane with a    second conditioning agent.

In a further aspect the present invention provides a thin film compositemembrane obtainable by any one of the methods defined herein.

In a further aspect the present invention provides a thin film compositemembrane obtained by any one of the methods defined herein.

In a further aspect the present invention provides a thin film compositemembrane directly obtained by any one of the methods defined herein.

TFC membranes of the invention are suitably made by interfacialpolymerisation, comprising a separating layer formed of a crosslinkedpolymer network possessing intrinsic microporosity. The TFC membranes ofthe invention can be used for gas separation and/or nanofiltrationoperations in aqueous and/or organic solvents. In particular, they canbe used for nanofiltration operations in organic solvents. An advantageof the membranes of the present invention is that a crosslinked polymernetwork possessing intrinsic microporosity is formed in situ during theinterfacial polymerisation reaction as the separating layer, whereasprior art thin film composite membranes with polymers of intrinsicmicroporosity are prepared by coating and are restricted to solublepolymers of intrinsic microporosity which are non-network polymers. Theuse of the composite membranes of the invention in nanofiltration withpolar aprotic solvents is advantageous when using a solvent stablesupport with respect to many of the prior art high free volume thin filmcomposite nanofiltration membranes, which are not stable in solventssuch as dimethylacetimide (DMAc), dimethylformamide (DMF),dimethylsufoxide (DMSO), tetrahydrofuran (THF), N-methyl-2-pyrrolidone(NMP), and dichloromethane (DCM) or require further crosslinking forsolvent stability. Another advantage of the membranes of the presentinvention is their thin separating layer (thickness in the order ofnanometers), with respect to many prior art high free volume thin filmcomposite membranes and TFC's with intrinsic microporosity, which areprepared by dip coating or solvent casting and have a separating layerthickness in the order of microns. Thinner separating layers give riseto higher permeabilities and require less material in the separatinglayer. Yet a further advantage of the membranes of the present inventionis that activating solvents may include polar aprotic solvents, andadditives may include a wide range of species in which the supportmembrane is stable. TFC membranes of the present invention may exhibithigher permeabilities and selectivities than known membranes for gasseparation and when mixtures of water and organic solvent are beingprocessed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the molecular weight cut off (MWCO) curve and flux of aTFC-IP-PIMs membrane prepared on a crosslinked P84 support. The TFCmembrane has been cured in the oven at 85° C. for 10 minutes.Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in acetone has been performed at 30 bar and 30° C.

FIG. 2 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has not been cured in theoven. Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in acetone has been performed at 30 bar and 30° C.

FIG. 3 shows the MWCO curve and flux of TFC-IP-PIMs membrane prepared ona crosslinked P84 support. The TFC membrane has been cured in the ovenat 85° C. for 10 minutes. Nanofiltration of a feed solution comprisingpolystyrene oligomers dissolved in methanol has been performed at 30 barand 30° C.

FIG. 4 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has not been cured in theoven. Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in methanol has been performed at 30 bar and 30° C.

FIG. 5 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has been cured in theoven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in DMF has been performed at30 bar and 30° C.

FIG. 6 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has not been cured in theoven. Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in DMF has been performed at 30 bar and 30° C.

FIG. 7 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has been cured in theoven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in THF has been performed at30 bar and 30° C.

FIG. 8 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has not been cured in theoven. Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in THF has been performed at 30 bar and 30° C.

FIG. 9 shows the MWCO curve and flux of a TFC-IP-PIMs membrane preparedon a crosslinked P84 support. The TFC membrane has been cured in theoven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in toluene has been performedat 30 bar and 30° C.

FIG. 10 shows the MWCO curve and flux of TFC-IP-PIMs membranes preparedon a crosslinked P84 support. The TFC membrane has not been cured in theoven. Nanofiltration of a feed solution comprising polystyrene oligomersdissolved in toluene has been performed at 30 bar and 30° C.

FIG. 11 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PEEK support membrane. The TFC membrane has been cured inan oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in THF has been performed at30 bar and 30° C.

FIG. 12 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PEEK support membrane. The TFC membrane has been cured inan oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in acetone has been performedat 30 bar and 30° C.

FIG. 13 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PEEK support membrane. The TFC membrane has been cured inthe oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in toluene has been performedat 30 bar and 30° C.

FIG. 14 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PEEK support membrane. The TFC membrane has been cured inan oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in heptane has been performedat 30 bar and 30° C.

FIG. 15 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PBI support membrane. The TFC membrane has been cured inan oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in THF has been performed at30 bar and 30° C.

FIG. 16 shows the MWCO curve and flux for a TFC-IP-PIMs membraneprepared on a PBI support membrane. The TFC membrane has been cured inan oven at 85° C. for 10 minutes. Nanofiltration of a feed solutioncomprising polystyrene oligomers dissolved in acetone has been performedat 30 bar and 30° C.

FIG. 17 shows the gas separation performance for a TFC-IP-PIMs membraneprepared on a PEEK support membrane. The membrane has been cured in anoven at 85° C. for 10 minutes. Gas permeation experiments were carriedout at 40, 50 and 60 psig. FIG. 17A shows CO₂/N₂ selectivity vs. CO₂permeability; FIG. 17B shows CO₂/CH₄ selectivity vs. CO₂ permeability,and FIG. 17C shows O₂/N₂ selectivity vs. O₂ permeability.

FIGS. 18A-C shows various concavity-containing monomers.

FIG. 18B shows various concavity-containing monomers.

FIG. 18C shows various concavity-containing monomers.

FIG. 19 shows examples of rigid monomers.

FIG. 20 shows the chemical structures of the monomers used for theinterfacial polymerization reaction in Exmaple 1.

DESCRIPTION OF VARIOUS EMBODIMENTS Definitions

As used herein, the terms “optionally” or “optional” means that thelater described event or action may or may not take place, and that thedescription includes examples where said event or action takes place andexamples where it does not.

The term “network polymer” is used herein to refer to a covalentlycross-linked 3-dimensional polymeric network. This is in contrast to a“non-network polymer” (or a “linear” polymer) in which the polymers donot have a covalently cross-linked 3-dimensional structure.

The term “microporosity” is used herein to refer to separating layer ofthe membrane comprising pores of less than or equal to 2 nm in size.

The term “intrinsic microporosity” is used herein to mean the networkpolymer provides a continuous network of interconnected intermolecularvoids (suitably of less than or equal to 2 nM in size), which forms as adirect consequence of the shape and rigidity (or concavity) of at leasta proportion of the component monomers of the network polymer. As willbe appreciated by a person skilled in the art, intrinsic microporosityarises due to the structure of the monomers used to form the networkpolymer and, as the term suggests, it is an intrinsic property of anetwork polymer formed from such monomers. The shape and rigidity of themonomer used to form the network polymer means that polymer possesses aninternal molecular free volume (IMFV), which is a measure of theconcavity of the monomers and is the difference between the volume ofthe concave monomer unity compared to that of the corresponding planarshape.

It is understood that the network polymers disclosed herein have acertain property (i.e. intrinsic microporosity). Disclosed herein arecertain structural requirements in the monomers used for giving apolymer performing the disclosed function, and it is understood thatthere are a variety of structures that can perform the same functionthat are related to the disclosed monomer structures, and that thesestructures will typically achieve the same result.

Disclosed are the monomers to be used to prepare the network polymers ofthe invention as well as the polymers themselves to be used within themethods disclosed herein. It is understood that when combinations,subsets, etc. of these monomers are disclosed, that while specificreference of each various individual and collective combinations andpermutation of these monomers may not be explicitly disclosed, each isspecifically contemplated and described herein. If a particular polymeris disclosed and discussed and a number of modifications that can bemade to a number of monomers are discussed, specifically contemplated iseach and every combination and permutation of the monomers and themodifications that are possible unless specifically indicated to thecontrary. Thus, if a class of monomers A, B, and C are disclosed, aswell as a class of monomers D, E and F and an example of a combinationpolymer A-D is disclosed, then even if each is not individually recitedeach is individually and collectively contemplated meaning combinationsA-E, A-F, B-D, B-E, B-F, C-D, C-E and C-F are considered disclosed.Likewise any subset or combination of these is also disclosed. Thus, forexample, the sub-group of A-E, B-F, and C-E would be considereddisclosed. This concept applies to all aspects of this applicationincluding, but not limited to, steps in methods of making and usingcompositions of the invention.

By the term “nanofiltration” it is meant a membrane process which willallow the passage of solvents while retarding the passage of largersolute molecules, when a pressure gradient is applied across themembrane. This may be defined in terms of membrane rejection R_(i), acommon measure known by those skilled in the art and defined as:

$\begin{matrix}{R_{i} = {\left( {1 - \frac{C_{Pi}}{C_{Ri}}} \right) \times 100\%}} & (1)\end{matrix}$where C_(P,i)=concentration of species i in the permeate, permeate beingthe liquid which has passed through the membrane, andC_(R,i)=concentration of species i in the retentate, retentate being theliquid which has not passed through the membrane. It will be appreciatedthat a membrane is selectively permeable for a species if R_(i)>0. It iswell understood by those skilled in the art that nanofiltration is aprocess in which at least one solute molecule i with a molecular weightin the range 100-2,000 g mol⁻¹ is retained at the surface of themembrane over at least one solvent, so that R_(i)>0. Typical appliedpressures in nanofiltration range from 5 bar to 50 bar.

The term “solvent” will be well understood by the average skilled readerand includes an organic or aqueous liquid with molecular weight lessthan 300 Daltons. It is understood that the term solvent also includes amixture of solvents.

By way of non-limiting example, solvents include aromatics, alkanes,ketones, glycols, chlorinated solvents, esters, ethers, amines,nitriles, aldehydes, phenols, amides, carboxylic acids, alcohols,furans, and polar protic and polar aprotic solvents, water, and mixturesthereof.

By way of non-limiting example, specific examples of solvents includetoluene, xylene, benzene, styrene, anisole, chlorobenzene,dichlorobenzene, chloroform, dichloromethane, dichloroethane, methylacetate, ethyl acetate, butyl acetate, methyl ether ketone (MEK), methyliso butyl ketone (MIBK), acetone, ethylene glycols, ethanol, methanol,propanol, butanol, hexane, cyclohexane, dimethoxyethane, methyl tertbutyl ether (MTBE), diethyl ether, adiponitrile, N,N dimethylformamide,dimethylsulfoxide, N,N dimethylacetamide, dioxane, nitromethane,nitrobenzene, pyridine, carbon disulfide, tetrahydrofuran,methyltetrahydrofuran, N-methylpyrrolidone, acetonitrile, water, andmixtures thereof.

The term “solute” will be well understood by the average skilled readerand includes an organic molecule present in a liquid solution comprisinga solvent and at least one solute molecule such that the weight fractionof the solute in the liquid is less than the weight fraction of thesolvent, and where the molecular weight of the solute is at least 20 gmol⁻¹ higher than that of the solvent.

Thin Film Composite Membranes

Thin film composite (also referred to as TFC) membranes will be familiarto one of skill in this art and include an entity composed of a thinfilm separating layer over a support membrane, where the supportmembrane is previously formed from a different material. TFC membranesare suitably formed by interfacial polymerisation.

Suitable support membranes can be produced from polymer materialsincluding polysulfone, polyethersulfone, poly(ether sulfone ketone),polyacrylonitrile, polypropylene, polyamide, cellulose acetate,cellulose diacetate, cellulose triacetate, poly(ether ethyl ketone),poly(pthalazinone ether sulfone ketone), a perfluoropolymer, polyimide,polybenzimidazole, perfluoropolymers, polyether ether ketone (PEEK),sulfonated polyether ether ketone (S-PEEK), or other polymeric materialsknown to those skilled in the art. Wherein, the polymer support membranemay be further crosslinked.

Preferably, suitable support membranes may be prepared from an inorganicmaterial such as by way of non-limiting example silicon carbide, siliconoxide, zirconium oxide, titanium oxide, aluminium oxides or zeolites,using any technique known to those skilled in the art such as sintering,leaching or sol-gel processes.

The polymer used to form the support membrane includes but is notlimited to polyimide polymer sources. The identities of such polymersare presented in the prior art, U.S. Pat. No. 0,038,306, the entirecontents of which are incorporated herein by reference. More preferably,the support membrane of the invention is prepared from a polyimidepolymer described in U.S. Pat. No. 3,708,458, assigned to Upjohn, theentire contents of which are incorporated herein by reference. Thepolymer, available from HP polymers GmbH, Austria as P84, is a copolymerderived from the condensation of benzophenone 3,3′,4-4′-tetracarboxylicacid dianhydride (BTDA) and a mixture of di(4-aminophenyl) methane andtoluene diamine or the corresponding diisocyanates,4,4′-methylenebis(phenyl isocyanate) and toluene diisocyanate.

Support membranes can be prepared following the methods described in GB2,437,519, the entire contents of which are incorporated herein byreference, and comprise both nanofiltration and ultrafiltrationmembranes. More preferably, the membranes of the invention used assupports are within the ultrafiltration range. The membrane supports ofthe invention may be crosslinked using suitable amine crosslinkingagents and the crosslinking method and time may be that described in GB2,437,519.

The support membrane is optionally impregnated with a conditioningagent. The term “conditioning agent” is used herein to refer to anyagent which, when impregnated into the support membrane prior to theinterfacial polymerisation reaction, provides a resulting membrane witha higher rate of flux. Any suitable conditioning agent may be used.Suitably, the conditioning agent is a low volatility organic liquid. Theconditioning agent may be chosen from synthetic oils (e.g., polyolefinicoils, silicone oils, polyalphaolefinic oils, polyisobutylene oils,synthetic wax isomerate oils, ester oils and alkyl aromatic oils),mineral oils (including solvent refined oils and hydroprocessed mineraloils and petroleum wax isomerate oils), vegetable fats and oils, higheralcohols (such as decanol, dodecanol, heptadecanol), glycerols, andglycols (such as polypropylene glycols, polyethylene glycols,polyalkylene glycols). Suitable solvents for dissolving the conditioningagent include water, alcohols, ketones, aromatics, hydrocarbons, ormixtures thereof. The first and second conditioning agents referred toherein may be the same or different.

In this invention, prior to the interfacial polymerization reaction, thesupport membrane is optionally treated with a first conditioning agentdissolved in a solvent to impregnate the support membrane. Suitably, thefirst conditioning agent is a low volatility organic liquid as definedabove.

Following treatment with the conditioning agent, the support membrane istypically dried in air at ambient conditions to remove residual solvent.

The interfacial polymerization reaction is generally held to take placeat the interface between the first reactive monomer solution, and thesecond reactive monomer solution, which form two phases. Each phase mayinclude a solution of a dissolved monomer or a combination thereof.Concentrations of the dissolved monomers may vary. Variables in thesystem may include, but are not limited to, the nature of the solvents,the nature of the monomers, monomer concentrations, the use of additivesin any of the phases, reaction temperature and reaction time. Suchvariables may be controlled to define the properties of the membrane,e.g., membrane selectivity, flux, separating layer thickness. At leastone of the monomers used in the reactive monomer solutions should havewell-defined concavity (i.e. concave shape). Monomers in the firstreactive solution may include, but are not limited to, polyphenols,polyamines, or mixtures thereof. The monomers in the second reactivesolution include but are not limited to polyfunctional acyl halides,polyfunctional haloalkylbenzenes, polyfunctional halogenated aromaticspecies, or mixtures thereof. The resulting reaction may form a networkpolymer separating layer on top of the support membrane, including butnot limited to a network polyester layer, a network polyether layer, anetwork polyamide layer, or a network layer that includes mixtures ofthese.

Although water is a preferred solvent for the first reactive monomersolution, non-aqueous solvents may be utilized, such as acetyl nitrileand dimethylformamide (DMF). Although no specific order of addition isnecessarily required, the first reactive monomer solution is typicallycoated on or impregnated into the support membrane first, followed bythe second reactive monomer solution being brought into contact with thesupport membrane. Although one or both of the first monomer and thesecond monomer may be applied to the porous support from a solution,they may alternatively be applied by other means such as by vapourdeposition, or neat.

A residue of a chemical species refers to the moiety that is theresulting product of the chemical species in a particular reaction orsubsequent chemical product, regardless of whether the moiety isactually obtained from the chemical species. Thus, an ethylene glycolresidue in a polyester refers to one or more —OCH₂CH₂O— units in thepolyester, regardless of whether the residue is obtained by reactingethylene glycol to obtain the polyester.

In this invention, the polymer matrix of the separating layer cancomprise any three-dimensional polymer network possessing intrinsicmicroporosity. In one aspect, the separating layer comprises at leastone of an aliphatic or aromatic polyamide, aromatic polyhydrazide,poly-benzimidazolone, polyepiamine/amide, polyepiamine/urea,poly-ethyleneimine/urea, sulfonated polyfurane, polyether, apolyether-amide, a polyether-urea, a polyester, a polyester-amide,polybenzimidazole, polypiperazine isophtalamide, or a polyimide or acopolymer thereof or a mixture thereof. The polymer selected to form theseparating layer can be formed by an interfacial polymerizationreaction.

It is an important feature of the present invention that at least one ofthe monomers participating in the interfacial polymerisation reaction isa molecule with a concave shape (i.e. concavity), preferably rigid andlinked to another monomer or monomers to form a polymer network withinwhich molecular rotation is preferably hindered. Concavity-containingmonomers include but are not limited to molecules containing aspiro-contorted centre, bridged ring moieties and sterically congestedsingle covalent bonds around which there is restricted rotation. Thesemolecules are also known as molecules with awkward shapes (i.e. thosethat pose packing problems due to their concavities). Structural unitswith well-defined cavities include but are not limited to1,1-spirobisindanes (e.g. 1, 3, 4-7, 19 in FIG. 18A-C),9,9-spirobisfluorenes (e.g. 16, 20 in FIGS. 18A-C), bisnaphthalenes(e.g. 2, 17 in FIGS. 18A-C) 1,1-spirobis,2,3,4-tetrahydro-naphthalenes(e.g. 11-14 in FIGS. 18A-C), and 9,10-ethanoanthracene (e.g. 8,9 inFIGS. 18A-C). Generally, the polymer network of the invention isprepared by reaction of two or more monomers, wherein at least one ofthe monomers possesses concavity. In one aspect the first monomer is adinucleophilic or polynucleophilic monomer and the second monomer is adielectrophilic or a polyelectrophilic monomer. Wherein, each monomercan have two or more reactive groups. Both electrophiles andnucleophiles are well known in the art, and one of skill in the art canchoose suitable monomers for the interfacial polymerisation reaction.The first and second monomers can be chosen so as to be able to undergoan interfacial polymerisation reaction to form a three-dimensionalpolymer network when brought into contact.

In FIGS. 18A-C, the reactive groups are shown as Z. Here Z may be anysuitable nucelophilic group such as hydroxyl or amine groups, andspecifically Z═—OH, —NH₂. Alternatively, Z may be any electrophilicgroup such as an acyl halide, specifically an acyl chloride, or anelectron withdrawing group that renders the monomer electrophilic.Suitable electron withdrawing groups include halogenated species F, Cl,Br, or I. 3, 4, 9 and 13 in FIGS. 18A-C show monomers where Z could be ahalogen. FIG. 19 shows examples of rigid monomers, which are optionalmonomers for the interfacial polymerization reaction. Such monomers maybe used individually or as mixtures with other monomers. Reactive groupsin FIG. 19 are assigned as Y. Here Y may be any suitable nucelophilicgroup such as hydroxyl or amine groups, and specifically Z═—OH, —NH₂.Alternatively, Z may be any electrophilic group such as an acyl halide,specifically an acyl chloride, or an electron withdrawing group thatrenders the monomer electrophilic. Suitable electron withdrawing groupsinclude halogenated species F, Cl, Br, or I. Species 2,5,8,9,11-22 inFIG. 19 show monomers where Y could be a halogen. For the purposes ofthe current invention, when Z is an electrophile or a leaving group thatmakes the monomer an electrophile, then Y is a nucleophile, and, when Zis a nucleophile, then Y is an electrophile or a leaving group thatmakes the monomer an electrophile. When Y is an electrophile, or anelectron withdrawing group that makes the monomer electrophilic,including F, Cl, Br, or I, then it may be particularly advantageous tocombine a rigid monomer from Chart 2 present in the second reactivemonomer solution with any of the monomers described above in Chart 1which are suitable for use in the first reactive monomer solution, suchas polyamines, or polyphenols, to form the separating layer.

In a further embodiment of this invention, the separating layercomprises a network comprised of but not limited to, a polyester, apolyether, a polyamide, a polyimide or a mixture thereof. The polyester,polyamide, polyether or polyimide can be aromatic or non-aromatic. Forexample, the polyester can comprise residues of a phthaloyl (e.g.terephthaloyl or isophthaloyl) halide, a trimesoyl halide, or a mixturethereof. In another example, the polyester can comprise residues of apolyphenol containing a spiro-contorted centre, or bridged ring moietiesor sterically congested single covalent bonds around which there isrestricted rotation, or a mixture thereof. Wherein, a concave monomermay include but is not limited to small oligomers (n=0-10) of a polymerwith intrinsic microporosity (PIM) containing nucleophilic orelectrophilic reactive groups. One of skill in the art can choosesuitable PIMs oligomers with reactive groups able to undergo aninterfacial polymerisation reaction, which include but are not limitedto polyphenols or polyamines (e.g. 25 and 26 in FIGS. 18A-C). In afurther embodiment, the separating layer comprises residues of atrimesoyl halide and residues of a tetraphenol with a spiro-contortedcentre. In a further embodiment, the film comprises residues oftrimesoyl chloride and5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI,monomer 1 in FIGS. 18A-C). In a further aspect, the film comprises thereaction product of trimesoyl chloride and the sodium salt of5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane(TTSBI).

The first reactive monomer solution may comprise an aqueous solution ofmonomer, and or a rigid monomer (see FIG. 19 for examples), and or aconcave monomer (see FIGS. 18A-C for examples), including, but notlimited to a polyphenol with concave shape. This aqueous polyphenolsolution may also contain other components, such as polyhydric compoundsas disclosed in U.S. Pat. No. 4,830,885. Examples of such compoundsinclude ethylene glycol, propylene glycol, glycerine, polyethyleneglycol, polypropylene glycol, and copolymers of ethylene glycol andpropylene glycol. The aqueous polyphenol solution may also contain polaraprotic solvents.

Aqueous monomer solutions may include, but are not limited to, anaqueous solution containing a salt of5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane(TTSBI), an alternative aqueous monomer solution, and/or combinationsthereof. Concentrations of solutions used in the interfacialpolymerzation may be in a range from about 0.01 weight % to about 30weight %. Preferably, concentrations of the interfacial polymerizationsolutions may be in a range from about 0.1% weight % to about 5 weight%. Further, aqueous monomer solutions may be rendered acidic or basic byaddition of appropriate reagents, so that the monomers are renderedsoluble as acidic or basic salts.

The second reactive monomer solution may contain monomers with orwithout concavity (see FIGS. 18A-C for examples), or/and oligomers ofPIMs, and or a rigid monomer (see FIG. 19 for examples). Monomers in thesecond solution, include, but are not limited to polyfunctional acylhalides such as trimesoyl chloride, or/and other monomers including butnot limited to polyfunctional haloalkylbenzenes, such as1,3,5-tris(bromomethyl)benzene, or/and rigid monomers with electrophilicor nucleopihilic reactive groups (assigned as Y) which can undergointerfacial polymerization (see FIG. 19 for examples of rigid monomers)including but not limited to polyfuncional halobenzenes, such as2,3,5,6-tetrafluoroterephthalonitrile, or a mixture thereof dissolved ina nonpolar solvent such as hexane, heptane, toluene or xylene. Further,the second reactive monomer solution may include, but is not limited to,a xylene solution of iso-phthaloyl dichloride, sebacoyl chloride, analternative organic monomer solution, and/or combinations thereof. Thedisclosed interfacial polymerization reaction time in step (b) may vary.For example, an interfacial polymerization reaction time may be in arange from about 5 seconds to about 48 hours.

Optionally, a capping step (c) may be carried out, in which unreactedgroups in the polymer network are capped to modify the surface chemistryof the composite membrane. It comprises contacting the membrane with asolution containing capping monomers, which may include alcohols,including but not limited to R—OH, Ar—OH, alcohols withsiloxane-substituents, alcohols with halo-substituents includingfluorine R_(F)OH, where R includes but is not limited to alkyl, alkene,R_(F), H, Si—O—Si. Amines may also be used as capping monomers and mayinclude but are not limited to R—NH₂, Ar—NH₂, amines withsiloxane-substituents, amines with halo-substituents including fluorineR_(F)NH₂, where R includes but is not limited to alkyl, alkene, R_(F),H, Si—O—Si. The capping medium may comprise a solution containing R-acylhalides or Ar-acyl halides, where R includes but is not limited toalkyl, alkene, R_(F), H, Si—O—Si.

A quenching step (d) includes contacting or treating the membrane afterthe interfacial polymerisation reaction with a quenching medium whichmay include but is not limited to water.

Optionally, a post treatment step (e) comprises curing the membrane withtemperature or with microwaves. Optionally, a post treatment step (f)comprises contacting the composite membranes prior to use fornanofiltration with an activating solvent, including, but not limitedto, polar aprotic solvents. In particular, activating solvents includeDMAc, NMP, DMF and DMSO. The activating solvent in this art is definedas a liquid that enhances the composite membrane flux after treatment.The choice of activating solvent depends on the separating layer andmembrane support stability. Contacting may be effected through anypractical means, including passing the composite membrane through a bathof the activating solvent, or filtering the activating solvent throughthe composite membrane.

The second conditioning agent applied in step (g) is optionallyimpregnated into the membrane by immersing the TFC membrane in a wateror organic solvent bath or baths comprising the second conditioningagent.

The resultant high flux semipermeable network TFC membranes withintrinsic microporosity of the invention can be used for gas separationor nanofiltration operations, particularly in nanofiltration in organicsolvents, and more particularly nanofiltration operations in polaraprotic solvents.

Gas separations include the separation of binary, ternary andmulticomponent mixtures including oxygen, nitrogen, hydrogen, carbondioxide, methane.

A variety of membrane shapes are useful and can be provided using thepresent invention. These include but are not limited to spiral wound,hollow fibre, tubular, or flat sheet type membranes. The membrane of thepresent invention can be configured in accordance with any of thedesigns known to those skilled in the art, such as spiral wound, plateand frame, shell and tube, and derivative designs thereof.

The following examples illustrate the invention.

EXAMPLES

In the following examples 1-3, nanofiltration performance of theinventive membranes was evaluated according to flux profiles andmolecular weight cut off (MWCO) curves. All nanofiltration experimentswere carried out at 30 bar using a cross-flow filtration system.Membrane discs, of active area 14 cm², were cut out from flat sheets andplaced into 4 cross flow cells in series. Permeate samples for fluxmeasurements were collected at intervals of 1 h, and samples forrejection evaluations were taken after steady permeate flux wasachieved. The MWCO was determined by interpolating from the plot ofrejection against molecular weight of marker compounds. The soluterejection test was carried out using a standard feed solution comprisedof a homologous series of styrene oligomers (PS) dissolved in theselected solvent. The styrene oligomer mixture contained 1-2 g L⁻¹ eachof PS 580 and PS 1090 (Polymer Labs, UK), and 0.01 g L⁻¹ ofα-methylstyrene dimer (Sigma-Aldrich, UK). Analysis of the styreneoligomers was done using an Agilent HPLC system with UV/Vis detector setat a wavelength of 264 nm. Separation was achieved using a reverse phasecolumn (C18-300, 250×4.6 mm). The mobile phase consisted of 35 vol %analytical grade water and 65 vol % tetrahydrofuran with 0.1 vol %trifluoroacetic acid.

Solvent flux (J) was determined by measuring permeate volume (V) perunit area (A) per unit time (t) according to the following equation:

$\begin{matrix}{J = \frac{V}{A \cdot t}} & (1)\end{matrix}$

The rejection (R_(i)) of markers was calculated from equation 2, whereC_(P,i) and C_(F,i) correspond to styrene concentrations in the permeateand the feed respectively.

$\begin{matrix}{R_{i} = {{\left( {1 - \frac{C_{P,i}}{C_{F,i}}} \right) \cdot 100}\%}} & (2)\end{matrix}$

In example 4, gas separation performance of the inventive membranes wasevaluated according to pure gas permeation measurements with CH₄, N₂, O₂and CO₂. The gas selectivities were measured for CO₂/N₂, CO₂/CH₄ andO₂/N₂. The gas permeabilities were measured with a soap-bubble meter atfeed pressures of 40, 50 and 60 psig. The gas selectivity of theinventive membranes was calculated by:

$\begin{matrix}{\alpha_{{CO}_{2}/N_{2}} = \frac{\left( {{Pg}/l} \right){CO}_{2}}{\left( {{Pg}/l} \right)N_{2}}} & (3)\end{matrix}$

Where α is the selectivity and P_(g) is the gas permeability.

Example 1

In the following example, membranes of the present invention are formedthrough interfacial polymerisation to form a polyester on a crosslinkedpolyimide support membrane, as follows:

Formation of Crosslinked Polyimide Support Membrane

A polymer dope solution was prepared by dissolving 24% (w/w) polyimide(P84 from HP Polymer AG) in DMSO and stirring overnight until completedissolution. A viscous solution was formed, and allowed to stand for 10hours to remove air bubbles. The dope solution was then cast on apolyester or polypropylene (Viledon, Germany) non-woven backing materialtaped to a glass plate using a casting knife (Elcometer 3700) set at athickness of 250 μm. Immediately after casting, the membrane wasimmersed in a water bath where phase inversion occurred. After 15minutes, it was changed to a new water bath and left for an hour. Thewet membrane was then immersed in a solvent exchange bath (isopropanol)to remove any residual water and preparation solvents.

The support membrane was then crosslinked using a solution ofhexanediamine in isopropanol, by immersing the support membrane in thesolution for 16 hours at room temperature. The support membrane was thenremoved from the crosslinking bath and washed with isopropanol for 1 hto remove any residual hexanediamine (HDA).

The final step for preparing the crosslinked polyimide support membraneinvolved immersing the membrane overnight into a conditioning agent bathconsisting of a volume ratio of 3:2 polyethylene glycol 400/isopropanol.The membrane was then wiped with tissue paper and air dried.

Formation of Thin Film Composite Membranes by InterfacialPolymerisation:

TFC membranes were hand-cast on the crosslinked polyimide supportmembrane through interfacial polymerization. The support membrane wastaped to a glass plate and placed in an aqueous basic NaOH solution(pH=13) of 2% (w/v)5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (98%,ABCR GmbH) for approximately 2 min. The phenoxide loaded supportmembrane was then rolled with a roller to remove excess solution. Thesaturated membrane support was then immersed in a solution of 0.1% (w/v)trimesoyl chloride (TMC, 98%, Sigma-Aldrich) in hexane. After 2 min ofreaction, the resulting membranes were withdrawn from the hexanesolution and rinsed with water (which corresponds to step (d) of theprocess defined herein, i.e. immersing the membrane into a quenchingmedium). The chemical structures of the monomers used for theinterfacial polymerization reaction are shown in FIG. 20.

Membrane identification codes for the TFC membranes prepared in thisExample are as follows:

Entry Membrane No. Membrane code 1 TFC membrane prepared on crosslinkedPI as TFC-PIMs-PI-n support 2 Cured TFC membrane prepared on crosslinkedTFC-PIMs-PI- PI as support oven-n

Where n identities membranes made in independent batch n.

Curing of TFC Membranes in the Oven (Step e)

A post-formation treatment step was carried out on the compositemembranes in which the membranes were cured in the oven at 85° C. for 10minutes.

Composite Membrane Performance

The performance of TFC membranes in DMF, THF, acetone, methanol andtoluene were evaluated with and without curing with temperature. Therejection curves and fluxes for the TFC membranes in DMF/PS solution,THF/PS solution, acetone/PS solution, methanol/PS solution andtoluene/PS solution with and without curing in the oven are shown inFIGS. 1 to 10. It is clear that curing the membranes at 85° C. increasesrejection.

Example 2

TFC membranes were prepared on PEEK support membranes, as follows:

Fabrication of Membrane Supports from Polyetheretherketone (PEEK):

A polymer dope solution was prepared by dissolving 12.3% (w/w) PEEK(VICOTE 704, a polyether ether ketone (PEEK) polymer, from Victrex) in79.4% methane sulfonic acid (MSA) and 8.3% sulfuric acid (H₂SO₄). Thesolution was stirred overnight until complete dissolution. A viscoussolution was formed, and allowed to stand for 10 hours to remove airbubbles. The solution was then cast on a polyester non-woven backingmaterial taped to a glass plate using a casting knife (Elcometer 3700)set at a thickness of 250 μm. Immediately after casting, the membranewas immersed in a water bath where phase inversion occurred. After 15minutes, it was changed to a new water bath and left for an hour. Thewet membrane was then immersed in a water bath to remove any residualpreparation solvents.

The final step for preparing the PEEK support membrane involvedimmersing the membrane overnight into a conditioning agent bathconsisting of a volume ratio of 3:2 polyethylene glycol 400/isopropanol.The membrane was then wiped with tissue paper and air dried.

TFC membranes were fabricated as per EXAMPLE 1, on top of the PEEKsupport membrane. The TFC membranes were cured in the oven at 85° C. for10 minutes as per EXAMPLE 1.

Membrane identification codes for the TFC membranes prepared in thisExample are as follows:

Entry No. Membrane Membrane code 3 Cured TFC membrane prepared oncrosslinked TFC-PIMs- PI as support PEEK-oven-n

Where n identifies membranes made in independent batch n.

Composite Membrane Performance

The performance of TFC membranes cured with temperature was evaluated inacetone, THF, toluene and heptane. The rejection curves and fluxes forthe cured TFC membranes in acetone/PS, THF/PS, toluene/PS, andheptane/PS solutions are shown in FIGS. 11, 12, 13 and 14 respectively.

Example 3

In this particular example TFC membranes were prepared on PBI supportmembranes, as follows:

Fabrication of membrane supports from polybenzimidazole (PBI):

A polymer dope solution was prepared by diluting a commercial dopesolution of 26 wt % PBI dissolved in DMAc (trade name: Celazole®) to 15wt % with DMAc. The solution was stirred for 4 h until completedissolution. A viscous solution was formed, and allowed to stand for 10hours to remove air bubbles. The solution was then cast on apolypropylene non-woven backing material taped to a glass plate using acasting knife (Elcometer 3700) set at a thickness of 250 μm. Immediatelyafter casting, the membrane was immersed in a water bath where phaseinversion occurred. After 15 minutes, it was changed to a new water bathand left for an hour. The wet membrane was then immersed in a water bathto remove any residual preparation solvents.

The final step for preparing the PBI support membrane involved immersingthe membrane overnight into a conditioning agent bath consisting of avolume ratio of 3:2 polyethylene glycol 400/isopropanol. The membranewas then wiped with tissue paper and air dried.

TFC membranes were fabricated as per EXAMPLE 1, on top of the PBIsupport membranes. The TFC membranes were cured in the oven at 85° C.for 10 minutes as per EXAMPLE 1. Membrane identification codes for theTFC membranes prepared in this Example are as follows:

Entry No. Membrane Membrane code 4 TFC membrane prepared on crosslinkedPBI TFC-PIMs-PBI- as support oven-n

Where n identifies membranes made in independent batch n.

Composite Membrane Performance

The performance of TFC membranes cured with temperature was evaluated inacetone and THF. The rejection curves and fluxes for the cured TFCmembranes in acetone/PS and THF/PS solutions are shown in FIGS. 15 and16 respectively.

Example 4

TFC membranes were fabricated as per EXAMPLE 2 (i.e. with PEEK assupport membrane without conditioning with PEG). The TFC membranes werecured in the oven at 85° C. for 10 minutes. Before the gas permeationmembranes were immersed in MeOH, followed by hexane and left to dryovernight.

Composite Membrane Performance

The gas separation performance of TFC membranes cured with temperaturewas evaluated for N₂, CO₂, CH₄ and O₂. The permeabilities vs.selectivities at different pressures are shown in FIG. 17.

What is claimed is:
 1. A thin film composite membrane suitable for usein nanofiltration operations in polar aprotic solvents, the thin filmcomposite membrane comprising: a support membrane that is stable inpolar aprotic solvents and is formed from a polymer selected from thegroup consisting of poly(ether ether ketone), polybenzimidazole andcrosslinked polyimide; and a separating layer disposed on top of thesupport membrane, wherein the separating layer is the interfacialpolymerisation product of first and second reactive monomers, at leastone of the first and second reactive monomers having concavity, whereinthe interfacial polymerization product is a network polyester polymerhaving intrinsic microporosity, said intrinsic microporosity beingdefined as a continuous network of interconnected intermolecular voids,said voids arising from the structure of the polymerised first andsecond reactive monomers.
 2. A membrane according to claim 1, whereinthe support membrane is impregnated with a conditioning agent that is alow-volatility organic liquid.
 3. A membrane according to claim 1,wherein the membrane is a temperature or microwave cured membrane.
 4. Amembrane according to claim 1, wherein the composite membrane is treatedwith an activating solvent being a polar aprotic solvent prior to use innanofiltration.
 5. A membrane according to claim 1, wherein the at leastone of the first and second reactive monomers having concavity isselected from a di- or poly-nucleophile, or a di- or poly-electrophilehaving two or more functional groups.
 6. A membrane according to claim1, wherein the at least one of the first and second reactive monomershaving concavity comprises at least one of a spiro-contorted centre, abridged ring moiety and a sterically congested single covalent bondsaround which there is restricted rotation.
 7. A membrane according toclaim 1, wherein the at least one of the first and second reactivemonomers having concavity is selected from one or more of the groupconsisting of 1,1-spirobisindanes, 9,9-spirobisfluorenes,bisnaphthalenes, 1,1-spirobis,2,3,4-tetrahydro-naphthalenes, and9,10-ethanoanthracene.
 8. A membrane according to claim 1, wherein inthe polymerization product adjacent reactive monomers having concavityare held in non-coplanar orientation.
 9. A membrane according to claim1, wherein the separating layer comprises the reaction product oftrimesoyl chloride and the sodium salt of5,5′,6,6′-Tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane.
 10. Amembrane according to claim 1, wherein the support membrane is acrosslinked polyimide support membrane and the polyimide used to formthe support membrane is at least one copolymer selected from the groupconsisting of: (a) the co-condensate of benzophenone3,3′,4,4′-tetracarboxylic acid dianhydride and a mixture of: (i)di(4-aminophenyl) methane and toluene diamine or (ii) a mixture of4,4′-methylenebis (phenyl isocyanate) and toluene diisocyanate; and (b)the condensate of 1H,3H-Benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone with5,5′-carbonylbis [1,3-isobenzofurandione],1,3-diisocyanato-2-methylbenzene and 2,4-diisocyanato-1-methylbenzene.11. A membrane according to claim 1, wherein the support membranecomprises crosslinks formed from the reaction of amines selected fromthe group consisting of aliphatic amines, aliphatic-aromatic amines, andaromatic amines with a polyimide polymer.
 12. A membrane according toclaim 2, wherein the conditioning agent is selected from the groupconsisting of one or more of polyolefinic oils, silicone oils,polyalphaolefinic oils, polyisobutylene oils, synthetic wax isomerateoils, ester oils and alkyl aromatic oils solvent refined oils,hydroprocessed mineral oils, petroleum wax isomerate oils, vegetablefats and oils, decanol, dodecanol, heptadecanol, glycerols,polypropylene glycols, polyethylene glycols, and polyalkylene glycols.13. A membrane according to claim 1, wherein the at least one of thefirst and second reactive monomers having concavity has any of thefollowing structures:


14. The thin film composite membrane of claim 1, wherein the separatinglayer has a thickness in the order of nanometers.